You know those prescription glasses that go from transparent to gray on a sunny day, Transitions? Wouldn't it be great to be able to do that with our windows — get clear unobstructed sunny windows on a cold day, but tint them during the hot summer days? Start-up nanotechnology company, RavenBrick, is doing just that with windows and walls, all without the use of electricity.

A great way to make a building is with passive solar design — design the building to take advantage of solar heat during cold weather and block out solar gain during warm weather. But doing this requires special window construction, louvers, shades and correctly sized overhangs, all which can end up blocking views and aren't necessarily temperature responsive.

Through the use of ever evolving nanotechnology, RavenBrick, has devised windows and walls that can adjust their performance based on the outside temperature, and all without the use of electricity!

The window product, RavenWindow, uses thermo-reflective filters to automatically transition from transparent to a darkened reflective state when outside temperatures rise. With this change, the window allows the building to benefit from the sun's light and heat, or block it to stay cool. The standard tint is a neutral gray, but other colors are also available. This product can also be retrofitted in existing window units using the reflective filter, which is laminated on existing glass.

For those looking to maintain privacy but provide natural light, the company also makes a window that will turn an opaque color, RavenLight. In its standard state, RavenLight is a translucent panel that allows filtered light to enter the interior, and when the outside temperate rises, RavenLight transitions to a white panel to block unwanted heat.

RavenBrick has also expanded beyond the glass and is also making the building shell responsive with phase change panels, RavenSkin. RavenSkin insulates like a normal wall, but can store the daytime sun heat and release it at night as the temperature changes.

All of these products have a higher initial cost compared to the standard counterparts, but in the long run the company claims they can reduce energy bills by up to 50%. For more information visit RavenBrick.com.